Manufacture of bimetal



Patented July 8, 19.47

MANUFACTURE F BIMETAL Joseph M. Goulding, Fairhaven, Mass., assigner toRevere Copper and Brass IncorporatedNew York, N. Y.,'a corporation ofMaryland Application August 4, 1942, Serial No. 453,494

My invention relates to welding metals by pressure while in the plasticcondition, particularly to welding metal elements in the manufacture ofso-called bi-metallic" sheets, strips, and the like. The invention,which has among its objects an improved method of Welding surfaces ofrelativelyv large area, and a method of making an improved assembly ofmetallic elements for use in the practice of such method, will be bestunderstood from the following description when read in the light of theaccompanying drawings of examples of such method and assembly.

The assembly is claimed in the divisional application Serial No.500,915, filed September 2, 1943.

In the drawings:

Fig. 1 is an isometric view of an assembly packet for use in thepractice of the improved method;

Figs, 2 and 3 are sections, on enlarged scales, on the lines 2 2 and3-3, respectively, of Fig. 1;

Fig. 4 illustrates a detail, on an enlarged scale;

Fig. 5 is a plan of a blank from which one of the covers of the assemblypacket according to Figs. 1 to 4 may be formed; and

Figs. 6 and l are sections corresponding to Fig. 3 showing modifiedforms of the assembly packet.

The present invention, without limitation thereto, is particularlyadapted for use in connection with forming so-called bi-metallic sheetsand strips comprising iron or steel sheets or strips clad on one or bothsides with another metal such as copper, or copper base alloys such`ascupronickel and gilding metal.

Generally speaking, the process is Aperformed by placing a rather thickslab, bar, or the like (for convenience in terminology hereinafter andin the appended claims termed a slab) of the cladding metal on a similarrather thick shape of steel, heating the slabs thus assembled until theybecome plastic enough to bewelded, and passing them in such plasticcondition between the pressure rolls of a mill for welding themtogether. The rolls of the mill are effective to elongate the slabs inrolling direction and thus reduce their thickness. By repeatedly passingthe slabs while they are hot between the rolls ofthe mill, strips ofconsiderable length and thin gauge may be formed. For example, a steelslab 24 inches wide, 48 inches long, and 3 inches thick, upon which isplaced a copper slab inch thick and approximately of the same width andlength as the steel slab, may be thus operated upon to produce a stripabout 24 inches wide and 36 feet long, in which the steel is about 0.335inch thick clad with copper about 0.04 inch thick.

According to one way of practising the inven- 10 Claims. (Cl. 29-188)tion, a steel slab l is treated thoroughly to clean its opposite faces3, say by pickling those faces and washing them to remove all traces ofthe pickling solution, or by subjecting the faces to grinding operationsfor rendering them clean and smooth. Not necessarily, but preferably,these faces are then coated with a flash of copper for preventing themfrom subsequently rusting or oxidizing. This flash of copper may beapplied, for example, by dipping the faces of the slab in a 1% solutionof sulphuric acid containing about 10 ounces copper sulphate per gallon.In contact with these faces of the steel slab may then be placed slabs 5of the cladding metal, the surfaces of the cladding metal which contactthe steel slab also being treated by pickling or grinding thoroughly toclean those surfaces. Over the slabs 5 may then be placed pan-likevcover members 'I having side walls 9. which side walls extend over theedges of the steel slab in closely adjacent relation thereto. The entireassembly may then. be placed in a press to force one pan-like covertoward the other and the slabs I and 5 into intimate contact, and, whilethe assembly is under pressure, the edges of the rims of the coversthroughout their entire extent may be electric welded to the edges ofthe steel slab, as indicated at Il in Figs. 1, 2 and 3, to hermeticallyseal the yjoints between them, this welding op/eration preferably beingperformed by electric arc deposition of a metal welding rod.

Preferably the slabs 5 of the cladding metal are of slightly shorterlength and narrower width than the steel slab I, as indicated in Figs. 2and 3,

to permit any slight creep of the slabs 5 relative to the slab i duringthe first rolling pass for welding the slabs together. The tight fit ofthe parts consequent upon the pan-like covers being welded in positionwhile the packet is under pressure will ordinarily prevent any slidingof the slabs 5 relative to the slab i but to insure against such slidingthe end portions of the slabs may, if desired, be pegged together, sayby use of dowels I3 driven into aligned drill holes in the slabs i and5, before the pan-like covers are placed in position. These dowels maybe of iron, and preferably are of small diameter, say in the order of 1Ainch, so as to have no particular resistance against shear when theassembly is heated to the welding temperature of the slabs. Commonly, asingle dowel at each end of the slabs will suffice.

The covers, which preferably are made of sheet I iron and are relativelythin, say about inch thick, are formed adjacent the peripheries of theslabs with franglble portions which will break and shaped, asillustrated in Fig. 4. The depth of the grooves is not critical so longas they provide a materially diminished cross-section of the bottom andside walls of the covers. With covers made of inch sheet ironsatisfactory results have been obtained in practice with grooves about0.04 inch deep.

Conveniently the vpan-like covers may be made from sheet iron blanks 2|in which the grooves il, I1 and I9 are formed. The blanks maybe bent onthe lines 23 and 2li to form pan-shaped covers after cutting out pieces21 between the bending lines 23 and 25 andthe corners ofthe blanks. Theedges 29 where the longitudinal and transverse side walls 9 of thecovers meet may be electric welded together for hermetically sealing thejoints at those edges, either prior to placing the covers in position,or, preferably. at the time the rims of the covers at the cover openingsare being welded to the steel slab l. v

To insure against the covers being welded to the slabs! they arepreferably made of unpickled or black sheet iron or steel, the scale onsuch iron or steel providing a layer preventing the covers from weldingto these slabs. Better to insure against this welding, the innersurfaces of the bottoms of the pan-like covers may be coated with alayer of colloidal graphite, say by mixing colloidal graphite powder andwater to form a thick paste and painting the inner surfaces of thebottoms of the covers with such paste. Pref erably, however, to preventany irregularities present in the bottoms of the covers from causingirregularities in the outer faces of thelslabs 5 when the packet isrolled, there are interposed between those faces and the bottoms of thecovers smooth sheets 3l of unpickled black iron or steel, the sides ofwhich sheets in contact with the slabs 5, or, if desired, both sidesthereof, are preferably coated with colloidal graphite. Also, ifdesiredfl the sheets 3i may be of rolled copper-silicon alloy, whichsheets do not necessitate the use of the colloidal graphite becausehaving thereon a film of silicon oxide they will not weld to either thecovers or the slabs 5. It will be observed that in all these instancesthere is interposed between the metal of the cover and that of the slaba layer which prevents the cover from welding to the opposed surface ofthe slab when the assembly is passed through the rolls of the mill.`

Instead of welding the side walls 9 of the panlikc covers to the steelslab. such walls may be suitable metal may the case with the claddingmetal. Further, when of requisite length to abut each other and enablethem to be welded together as indicated at 33 in Fig. '1, or may beslightly shorter, as shown in Fig. 6, to enable them to be welded toboth each other and the steel slab, as indicated at 35 in Fig. 6.

After the packet is formed it may be placed in a furnace and heated tothe welding temperature of the slabs, say to about`1850 F. when theslabs 5 are of copper, at which welding temperature all the slabs are ina plastic condition.

During the heating of the packet in the furnace 75 another to form `thearea or areas of 4 and after it is removed therefrom in a heatedcondition the covers protect the steel slab from oxidizing and scaling,which scaling if it occurred would prevent the slabs from weldingtogether during the subsequent welding operation. The heated packet maythen be 'removed from the furnace and passed between the pressure rollsof a rolling mill to weld the slabs together, and by repeatedly passingthem between the rolls the welded together slabs may be reduced to formlong relatively thin strips of the bi-metal.

During the first or second pass of the packet between the rolls of themill the consequent elongation of the slabs and cooling of the coversare effective to rupture the covers at the above described frangibleportions thereof, permitting A the covers to be stripped from the slabsat that ,tact with the relatively cool rolls of the mill, cool morerapidly than the slabs, which cooling is augmented by the fact that thethin gas film between the bottom of each cover and the adjacent face ofthe slab acts as an insulating layer to diminish conduction of heat fromthe slabs 5 to the cover, as likewise act the sheet 3l and the graphitelayer or layers when either is employed between the cover and slab 5.The material of the covers at the bottoms of the grooves I5, il and i9consequently ruptures when the slabs are elongated, because the covers,particularly their bottoms, having somewhat cooled resist elongation ltothe extent that the slabs elongate, while the transverse side Walls ofthe covers are forced to move with the ends of the slabs, and thoseportions of the longitudinal side walls of the covers not electricwelded to the steel slabs have no particular tendency to elongate atall.'

After the slabs are reduced by the rolling operation to form the abovedescribed relatively thin strips of bi-metal, the ends and sides of saidstrips may be trimmed by a splitting-operation to removefthe remnants ofthe covers and the weld metal for securing the covers in position, itbeing understood that the rolled strips almost always are subjected tosuch a trimming operation after being rolled, and therefore removing theremnants of the covers and the weld metal in this way involves noadditional operation.

In place of a steel slab,a slab of any other be employed, as is likewisedesired but one side of the steel or other base slab may be clad withanother metal, in which case it is necessary to employ but one pan-likecover. which latter may be placed over the slab of cladding metal and bewelded at the cover opening to the edges ofthe steel or other base slabas shown by Figs. 1,l 2 and 3, that is to say, in s uch case one of thecovers of these gures would be omitted. It will be observed` that in allthese cases, whether the steel or other base slab is to beclad on one orboth sides, the pan-like cover or covers employed in substance cause theslabs to be boxed in a container for excluding air and vgases fromseparation of the slabs.

It will be understood that, within the scope of the appended claims,wide deviations may be made from the formsof the invention hereindescribed without departing from the spirit of the invention.l

I claim: 1. The method of Welding one metal slab to bi-metal whichcomprises hermeticaliy boxing the slabs witha face of one in* weldingrelation to that of the other in a sheet metal container havinglongitudinal and transverse side walls jointly surrounding the edges ofl,

both slabs, and also having a wall connected to said side walls andopposed to the outer face of one of the slabs, which container also hasfrangibleportions adjacent said edges of the slabs, whereby to excludeair and gases from the area of separation of the slabs and provide thecontainer with frangible portions adjacent said edges ot the slabsbreakable upon the slabs being-elongated; heating the boxed assemblythus formed to the Welding temperature of the slabs while maintainingthem hermetically boxed; and pressing the heated slabs toward each otherand welding their opposed faces together and elongating them by passingthe heated hermetically boxed assembly flatwise between the rolls of amill, whereby to rupture the walls of the container at the frangibleportion thereof upon the welded together slabs being so elongated.

2. The method according to claim 1 which includes placing an insulatinglayer between the container and the adjacent boxed slab face forinsuring against welding of said container to said face.

3. The method of welding one metal slab to another to form bi-metalwhich comprises boxing the slabs with a lace of one in welding relationto that of the other in a sheet metal container jointly surrounding theedges of both slabs, and

also having a wall connected to said side walls and opposed to the outerface of one of the slabs, which container .is substantially continuouslygrooved adjacent said edges of the slabs, whereby to exclude air andgases from the area of separation of said slabs and provide thecontainer with frangible portions adjacent said edges of the slabsbreakable upon the slabs being elongated; heating the boxed assemblythus formed to the welding temperature of the slabs; and pressing theheated slabs toward each other and Welding them together and elongatingthem by passing the heated boxed assembly ilatwise between the rolls ofa mill, whereby to rupture the walls of the container at said grooveupon the welded together slabs being so elongated.

4. The method according .to claim 3 in which the slabs are boxed in acontainer each side wall of which that extends lengthwise of the slabshas a groove extending lengthwise of said slabs from adjacent one end ofsaid wall to the other, and which container also has grooves connectingthe adjacent ends of the rst mentioned grooves, the second mentionedgrooves extending across a wall of said container which contacts with amill roll wheigythe boxed slabs are passed between the rolls of a mill.

5. The method according to claim 3 in which the slabs are boxed in acontainer each side wall of which that extends lengthwise of the slabshas a -groove extending lengthwise of said slabs from adjacent one endof said wall to the other, and which container also has groovesconnecting the adjacent ends of the first mentioned grooves, the secondmentioned grooves extending across a wall of said container whichcontacts with a mill roll when the boxed slabs are passed between therolls of a mill, the method also including placing an insulating layerbetween said roll contacting wall of the container and the adjacent slabface for insuring against said wall welding to said face.

v8. The method of welding one metal slab to anj other to form bi-metalwhichy comprises assembling the slabs with a face of one in weldingrelation to that of the other with a pan-like sheet metal cover overthem in such wise that the bottom of the cover is opposed to'al face ofone of the slabs and the side walls thereof surround the edges of bothslabs, the walls oi the cover'adjacent said edges of the slabs havingfrangible portions breakable upon the slabs -being elongated; pressingthe cover and slabs together, and, while pressed together, securing'theside walls of the cover to the slab adjacent the cover opening inhermetically sealed relation; heating the assembly to the weldingtemperature of the slabs while maintaining such hermetically sealedrelation; and welding said slabsy together and elongating them bypassing the heated assemblybetween the rolls of a mill with the bottomof the cover in contact with one of such rolls, whereby to rupture thefrangible portion of said cover upon the welded together slabs being soelongated.

7. 'I'he method according'to 'claim 6 which 'includes hermeticallywelding the side walls of the cover to the slab adjacent the coveropening.

v8. The method of welding one metal slab to another to form bi-metalwhich comprises assembling the slabs with a face of one in weldingrelation to that of the other with a pan-like sheet metal cover overthem in such wise that the bottom oi' the cover is opposed to a face ofone of the slabs and the side walls thereof surround the edges of bothslabs, the walls of the pan operatively having a continuous grooveextending about it adjacent the peripheries of the slabswhereby saidwalls will rupture at said groove upon the slabs being elongated;vpressing the-cover and slabs together, and, while pressed together,securing the side walls of the pan-like cover to the slab adjacent thecover opening in hermetically sealed relation; heating the assemblytothe welding temperature of the slabs; and welding said slabs togetherand elongating them by passing the heated assembly between the rolls ofa mill with the bottom of the cover in contact with one of such rolls,whereby to ru ture said walls at said groove upon the welded togetherslabs being so elongated.

9. The method of welding metal slabs to each of opposite faces,respectively, of a third slab to form bi-metal which comprisesassembling the three slabs with their faces in welding relation withlseparate pan-like sheet metal covers over each l of the two outer slabs,respectlvely,land adjacent portions of the third slab in such wise thatthe bottoms of the covers are opposed to the outer faces of the outerslabs .and the side walls of the covers surround the edges of the outerslabs and the third slab, the side walls of which pan-like covers havefrangible portions adjacent the peripheries of said slabs breakable uponsaid slabs being elongated; welding the side walls of the pan-likecovers to the edges of said third slab. in hermetically sealed relationthereto, whereby to exclude air and gases from the areas of separationof said slabs; heating the assembly to the welding temperature of theslabs 4while maintaining such hermetically sealed relation; and weldingthe slabs together and elongating them by passing of opposite faces,respectively, o! a third slab to form bi-metal which comprisesassembling the' three slabs with their faces in welding relation withseparate pan-like sheet metal covers over each of the two outer slabs,respectively, and adjacent portions of the third slab ln such wise thatthe bottoms of the covers are opposed to the outer 'faces ci the outerslabs and the side walls of the covers surround ythe edges oi.' theouter slabs andl the thirdslab, the side walls oi which pan-like covershave frangible portions adjacent the peripheries of said slabs breakableupon said slabs being elongated; welding the side walls of the pan-likecovers to each other at their rims in hermetically sealed relation,whereby to exclude air and gases from the areas of separation of said[slabs: heating the assembly tothe welding temtions oi said covers uponthe welded together slabs being so elongated. 4

JQSEPH M. GOULDING.

REFERENCES CITED The following references are of record inthe 2 Number ville of this patent:

. yUNITED STATES PATENTS Number Name Date Acre May 1, 1934 Chace Jan.31, 1939 Plttevil Apr. 5, 1921 Meyer Nov. 18, 1880 Ingersoll May 4, 1937Armstrong Mar. 23, 1937 Trembour Dec. -14, 1937 Gritchett Oct. 2, 1934Huston- Dec. 24, 1940 Huston Feb. 14, 1939 FOREIGN PATENTS Country DateGreat Britain Jan. 9, 1920

